Microscopic structural changes during the freeze cross-linking reaction in carboxymethyl cellulose nanofiber hydrogels
Microscopic structural changes during the freeze cross-linking reaction in carboxymethyl cellulose nanofiber hydrogels
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DOI：
10.1016/j.carpta.2022.100251
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发表时间：
2022-10-04
影响因子：
5.5
通讯作者：
Ohzawa, Tatsuhiko
中科院分区：
文献类型：
--
作者：
Miura, Daisuke;Sekine, Yurina;Ohzawa, Tatsuhiko
冷冻交联增加了羧甲基纤维素凝胶（CMCF）的机械强度。研究了CMCF水凝胶在冷冻交联过程中的结构变化。不同反应时间制备的CMCF水凝胶的SEM图像显示，CMCF水凝胶在交联反应的初始状态（t？？1 h）由于原始CMCF而具有纤维状结构。随着反应的进行（t？12 h）时，纤维状结构消失，形成平均厚度为1.5 μ m的片状结构。0.2 ?? m被观察到。XRD图谱表明，该片材由纤维素II的稳定结晶结构组成，其中CMCF沿沿着（110）面排列。还证实，使用酸性水溶液如柠檬酸、DL-苹果酸、乳酸或氯化氢作为交联剂产生具有片状结构和高压缩强度的CMCF水凝胶。另一方面，当使用碱性水溶液如柠檬酸三钠、三聚磷酸盐或尿素作为交联剂时，形成具有不均匀纤维结构的脆性CMCF水凝胶。
Freeze cross-linking increases the mechanical strength of carboxymethyl cellulose nanofiber (CMCF) hydrogels. The structural changes of CMCF hydrogels during the freeze cross-linking reaction were investigated. The SEM images of CMCF hydrogels prepared with different reaction times showed that the CMCF hydrogel in the initial state of the cross-lining reaction (t ??? 1 h) has a fibrous structure due to the original CMCF. As the reaction progressed (t ??? 12 h), the fibrous structure was no longer present and a sheet structure with the average thickness of 1.5 ?? 0.2 ??m was observed. The XRD profiles indicated that the sheet consisted of a stable crystalline structure of cellulose II, in which CMCF was aligned along the (110) plane. It was also confirmed that using acidic aqueous solutions such as citric acid, DL-malic acid, lactic acid, or hydrogen chloride, as cross-linking agents yields CMCF hydrogels with the sheet structure and high compressive strength. On the other hands, when alkaline aqueous solution such as trisodium citrate, tripolyphosphate, or urea were used as cross-linking agents, brittle CMCF hydrogels with inhomogeneous fibrous structures were formed.